The election of Democrat Doug Jones to the U.S. Senate complicates — and could all but doom — Republican efforts to score any big wins for President Donald Trump.

The narrowing of the Senate Republicans’ already-slim majority represents a huge loss to the GOP, which failed this year to deliver on a campaign promise to repeal Obamacare and has struggled to pass spending legislation.

Yet Jones’ victory over Republican Roy Moore also comes as a relief to Majority Leader Mitch McConnell, R-Ky. McConnell championed Moore’s primary opponent and called on the nominee to leave the race after several women came forward to complain that Moore had pursued them as teenagers.

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Democrat Doug Jones won Alabama's special Senate election on Tuesday, beating back history, an embattled Republican opponent and President Donald Trump, who urgently endorsed GOP rebel Roy Moore despite a litany of sexual misconduct allegations. Moore, meanwhile, refused to concede and raised the possibility of a recount during a brief appearance at a sombre campaign party in Montgomery. "It's not over," Moore said. He added, "We know that God is still in control." AP

The GOP struggled throughout 2017 when it controlled 52 of the 100 seats in the Senate. Tuesday’s loss is sure to boost the influence of maverick Republican senators such as Susan Collins of Maine, who was one of three Republicans to oppose the Senate’s latest effort to repeal the 2010 Affordable Care Act.

Collins has played a critical role in the current tax debate as well, insisting that she has an agreement with leadership that legislation to reinstate cost-sharing payments to insurance companies passes before the tax bill is complete. House conservatives have opposed the measure, but Collins says she’s talked to President Donald Trump about getting it done.

House and Senate Republicans are trying to hammer out the details on a sweeping tax plan with the goal of delivering it to the White House for Trump’s signature by Christmas. McConnell insisted Tuesday that the unusual speed of the negotiations is unrelated to the prospect of losing a critical vote.

That vote, though, could matter in 2018 as programs that have traditionally attracted some Republican support will be on the schedule. Immigration reform is expected to be on the Senate’s agenda. Conservatives will push for more spending restraint. Environmental programs will be debated.

Sen. Luther Strange, R-Ala., who lost to Moore in the Republican primary and backs the tax bill, is expected to stay through the end of the session, McConnell said. Jones likely would not be sworn in until late December or early January.

Sen. John Kennedy, R-La., downplayed the loss of a Republican vote, noting its already difficult for McConnell to garner enough Republicans to get major legislation passed.

“It will mean we have one less vote,” Kennedy said of Moore’s loss."We have a lot of entrepreneurs, politically speaking. Every now and then we have a free range chicken that will break loose."

Republican candidate for senate, Roy Moore, rode his horse, Sassy, to the polls on Dec. 12 to cast his ballot. “This is a very important race for our country, for our state, and for the future,” Moore said. AP

“Things happen up here, someone passes on and you lose a seat, sometimes you have a special election and you lose a seat,” Shelby said. “But the 2018 election will decide who’s in control of the Senate and I think it’s going to be us.”

Moore would not necessarily have been a guaranteed Republican vote on anything. He railed against McConnell and establishment Republicans in the Alabama Republican primary and told Fox News in September that he wouldn’t have voted for the Republican health care plan.

Democrats, though, saw both momentum and a crucial new vote. Sen. Cory Booker, D-N.J., who campaigned for Jones in Alabama, suggested the victory could “elevate” a fractious Senate.

“I think we’ve got to figure out a way to come together,” Booker said.

Ross Baker, a Rutgers University political science professor who has written about the Senate, suggested Moore’s loss was a “mixed curse” for Senate Republicans.

“They don’t get the seat, but they also don’t have to explain him,” Baker said of Moore. “They won’t have to answer ‘Why did you let this guy in?’ They won’t have to run with him around their necks.”

It’s also not impossible that Jones, who distanced himself from national Democrats as he campaigned, could at times side with Republicans, given that he represents a deeply red state.

“He’d be an oddity in a liberal caucus,” Baker said of Jones. “Certainly (Senate Minority Leader Chuck) Schumer would do everything he can to protect him, but he can’t steer the entire caucus’ needs around the needs of Doug Jones in Alabama.”